Screening of MgO- and CeO_2-Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C_(2+) Hydrocarbons

The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM) have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O2-2) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts. The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts, although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.

Porous ternary complex metal oxide nanoparticles converted from core/shell nanoparticles

We demonstrate an easy and scalable low-temperature process to convert porous ternary complex metal oxide nanoparticles from solution-synthesized core^shell metal oxide nanopartides by thermal annealing. The final products demonstrate superior electrochemical properties with a large capacity and high stability during fast charging/discharging cycles for potential applications as advanced lithium-ion battery （LIB） electrode materials. In addition, a new breakdown mechanism was observed on these novel electrode materials.

Synergetic ternary metal oxide nanodots-graphene cathode for high performance zinc energy storage

Zinc-based electrochemistry ene rgy sto rage with high safety and high theoretical capacity is considered to be a competitive candidate to replace lithium-ion batteries.In electrochemical energy storage,multimetal oxide cathode materials can generally provide a wider electrochemical stability window and a higher capacity compared with single metal oxides cathode.Here,a new type of cathode material,MnFe2Co3O8 nanodots/functional graphene sheets,is designed and used for aqueous hybrid Zn-based energy storage.Coupling with a hybrid electrolyte based on zinc sulfate and potassium hydroxide,the asfabricated battery was able to work with a wide electrochemical window of 0.1~1.8 V,showed a high specific capacity of 660 mAh/g,delivered an ultra high energy density of 1135 Wh/kg and a scalable power density of 5754 W/kg(calculated based on the cathode),and displayed a long cycling life of 1000 cycles.These are mainly attributed to the valence charge density distribution in MnFe2Co3O8 nanodots,the good structural strengthening as well as high conductivity of the cathode,and the right electrolyte.Such cathode material also exhibited high electrocatalytic activity for oxygen evolution reaction and thus could be used for constructing a Zn-air battery with an ultrahigh reversible capacity of 9556 mAh/g.

Ternary Metal–Organic Framework Derived 2D Fe_(2)O_(3)/Co_(3)O_(4)/NiO/NC Heterostructured Nanosheets for Super Lithium Storage

Fe_(2)O_(3)/Co_(3)O_(4)/NiO/NC nanosheets have been successfully prepared via a two-step annealing process of ternary metal coordination polymer. Attributing to the synergistic effects of the multiple metal oxides and the unique 2D nanosheet structure, the improved electrical conductivity and effective electron/ion transfer enables Fe_(2)O_(3)/Co_(3)O_(4)/NiO/NC electrode to exhibit excellent electrochemical properties with outstanding rate capacity and cycling stability. This work may pave the way to construct ternary metal oxide electrode material with an excellent electrochemical performance by introducing multiple metal oxides.

Self-template formation of porous yolk-shell structure Mo-doped NiCo2O4 toward enhanced lithium storage performance as anode material

Hollow ternary metal oxides have shown enormous potential in lithium-ion batteries(LIBs),which is ascribed to their complex chemical composition,abundant active defect sites,and the synergy effect be-tween metals.In this work,we synthesized Mo-doped NiCo_(2)O_(4) porous spheres with yolk-shell structure by using a simple self-templating method.Surprisingly,other than the yolk-shell structure we had ob-tained,the inner core of the yolk-shell was also porous,which could fully enhance the electrolyte infil-tration and promote the transmission of lithium ions(Li+)and electrons(e−).The diameter of the porous core in the yolk-shell sphere was about 530 nm,and the outer shell’s thickness was up to 110 nm.In addition,the unique pores in the core appeared in the diameter of about 85 nm.With this structure,the volume expansion of the anode could be well inhibited during charge/discharge.It exhibited prominent electrochemical performance with high reversible capacity(1338 mA h g^(−1) at 100 mA g^(−1)),satisfactory cycle life(1360 mA h g^(−1) after 200 cycles at 100 mA g^(−1)),and exceptional rate capability(820 mA h g^(−1) at 2000 mA g^(−1))as anode material in LIBs.

Synthesis of hierarchical mesoporous Ln_(2)Ti_(2)O_(7)(Ln=Y,Tb-Yb)pyrochlores and uranyl sorption properties

Mesoporous structured metal oxides exhibit many active applications.However,the synthesis of crystalline metal oxides with a ternary composition while maintaining satisfactory pore features is challeng-ing.Typically,high temperatures are required which inhibit control of pore structure properties including surface area,pore volume,and pore size.Herein,the synthesis of ternary metal oxides Ln_(2)Ti_(2)O_(7)pos-sessing pyrochlore crystal structure is achieved using a novel technique which combines‘soft’and hard colloid templating strategies.The formed materials are of submicron size and composed of∼25-30 nm product‘building blocks’with good chemical and phase stability.The polycrystalline powders have a high specific surface area(up to 70 m^(2)·g^(-1))and pore volume(∼0.35 cm^(3)·g^(-1))which result in a good adsorp-tion capacity(U uptake closing to 60 mg·g^(-1)).Remarkably,the material exhibits a significant portion of mesopores(mainly 10-40 nm)which facilitate fast adsorption of the cations due to high accessibility.The synthetic methodology described herein produces highly homogenous powders and can be applied to other compositions and structures.

Sulfur dioxide sensing properties of MOF-derived ZnFe_(2)O_(4) functionalized with reduced graphene oxide at room temperature

In this paper,ZnZnFe_(2)O_(4) nanorods were prepared using Zn/Fe metal organic framework(MOF)as precursors,and ZnZnFe_(2)O_(4)/reduced graphene oxide(rGO)was prepared by hydrothermal method.The morphology and composition of the ZnZnFe_(2)O_(4)/rGO nanocomposite were characterized,and the results showed that the MOF-derived ZnZnFe_(2)O_(4) nanorods are uniformly modified on the surface of rGO.The ZnZnFe_(2)O_(4)/rGO nanocomposite exhibits better SO_(2) gas sensing performance than the single ZnZnFe_(2)O_(4) nanorods at room temperature.The sensing characteristics of single ZnZnFe_(2)O_(4) film sensor,single rGO film sensor and ZnZnFe_(2)O_(4)/rGO composite film sensor at SO_(2)gas concentration(1×10^(-6)-100×10^(-6))were tested.The response of ZnZnFe_(2)O_(4)/rGO composite sensor can reach 18.32%at room temperature.Compared with single ZnZnFe_(2)O_(4) and rGO film sensors,the ZnZnFe_(2)O_(4)/rGO composite sensor has better transient response,good sensitivity and selectivity.In this work,the improvement of the sensor performance is not only due to the p-n heterostructure between ZnZnFe_(2)O_(4) nanorods and rGO nanosheets,but also to the excellent electrical properties of rGO.It provides a new idea for the detection of SO_(2) at room temperature.

Nanostructured BiVO4 Derived from Bi-MOF for Enhanced Visible-light Photodegradation

BiVO4,a promising visible-light responding photocatalyst,has aroused extensive research interest because of inexpensiveness and excellent chemical stability.However,its main drawback is the poor photoinduced charge-transfer dynamics.Building nanostructures is an effective way to tackle this problem.Herein,we put forward a new method to prepare nanostructured BiVO4 from Bi-based metal-organic frameworks[Bi-MOF(CAU-17)]precursor.The as-prepared material has a rod-like morphology inherited from the Bi-MOF sacrificial template and consists of small nanoparticle as building blocks.Compared with its counterparts prepared by conventional methods,MOF-derived nanostructured BiVO4 shows better light absorption ability,narrower bandgap,and improved electrical conductivity as well as reduced recombination.Consequently,BiVO4 nanostructure demonstrates high photocatalytic activity under visible light towards the degradation of methylene blue.Methylene blue can be degraded up to 90%within 30 min with a reaction rate constant of 0.058 min-1.Moreover,the cycling stability of the catalyst is excellent to withstand unchanged degradation efficiency for at least 5 cycles.